Dietary arginine supplementation decreases plasma cortisol levels and modulates immune mechanisms in chronically stressed turbot (Scophthalmus maximus)

Abstract

Repeated handling was employed in this study as a chronic stressor to verify whether its attributed immunosuppressive effects could be minimized by dietary arginine supplementation. Therefore, turbot (Scophthalmus maximus) were air-exposed for 3 min (mild hypoxia) every other day during 15 or 60 days (handled) or left undisturbed (control). In addition, control and handled specimens were fed one of three diets with graded levels of arginine (6, 7 and 11 g 16 g À1 N; Arg 6, Arg 7 and Arg 11, respectively). Repeated handling increased plasma cortisol levels in handled fish fed the Arg 6 diet when compared with control groups, while those levels decreased in handled fish fed Arg 7 and Arg 11 diets after both 15 and 60 days. Moreover, repeated handling stress decreased nitric oxide production, lysozyme activity and peripheral lymphocyte numbers after 15 days, while more profound effects were observed after 60 days. Furthermore, circulating monocytes, nitric oxide production and humoral parameters increased in both control and handled fish fed arginine supplements. In conclusion, dietary arginine supplementation may present valuable effects in chronically stressed turbot by decreasing plasma cortisol levels and enhancing most aspects of the innate immune mechanisms assessed after 60 days.

European Sea Bass (Dicentrarchus labrax) Immune Status and Disease Resistance Are Impaired by Arginine Dietary Supplementation

“…Several studies have considered arginine administration as a strategy that improves the immune response, and, more specifically, the inflammatory process: in fish, previous studies have shown that several factors of the innate immune response, such as the extracellular superoxide anion production, lysozyme activity and neutrophil oxidative radical production were stimulated upon dietary arginine supplementation [ 26 ]. In turbot ( Scophthalmus maximus ), high rearing density caused immunosuppressive effects that were counteracted by dietary arginine supplementation [ 27 ]. Furthermore, Chen and co-authors [ 28 ] suggested that arginine contributed to an enhanced immune response of Jian carp and higher survival against Aeromonas hydrophila based on the up-regulation of pro-inflammatory gene expression.…”

Beneficial roles of feed additives as immunostimulants in aquaculture: a review

“…In a later paper, they found that plasma cortisol levels were reduced in stressed turbot ( Scophthalmus maximus ) after arginine supplementation (Costas et al . ). Both arginine and lipopolysaccharide exposure induce nitric oxide production in head kidney macrophages (Buentello & Gatlin ; Tafalla & Novoa ).…”

Differential effects of exposure to parasites and bacteria on stress response in turbotScophthalmus maximussimultaneously stressed by low water depth

“…Control fish under LWD displayed increased levels of cortisol in plasma compared with fish under NWD conditions. No prior studies addressed this issue in S. maximus though the response was comparable with the changes induced in the same species by other stressors such as handling (Costas et al, ) or exercise (Van Ham et al, ). The magnitude of the increase was also comparable with that observed in comparable studies in different fish species under HSD.…”